From 1983 through 1989, the incidence of hepatitis A in the
United States increased 58% (from 9.2 to 14.5 cases per 100,000
population). Based on analysis of hepatitis A cases reported to
CDC's national Viral Hepatitis Surveillance Program in 1988, 7.3%
of hepatitis A cases were associated with foodborne or waterborne
outbreaks (1). This report summarizes recent foodborne-related
outbreaks of hepatitis A in Alaska, Florida, North Carolina, and
Washington.Alaska

Between June 18 and July 20, 1988, 32 serologically confirmed
hepatitis A cases among persons who resided in or had visited
Peters Creek, Alaska (population 4000), were reported to the
Alaska Department of Health and Social Services (Figure 1).
Patients ranged in age from 1 to 54 years (median: 13 years).
Between July 8 and August 14, 23 additional (secondary) cases
occurred among household contacts of the original patients.

To examine potential sources of infection, the Alaska
Department of Health and Social Services conducted a case-control
study of the first 14 reported patients and 22 asymptomatic
household members. All 14 patients and seven (32%) household
members had consumed an ice-slush beverage purchased from a local
convenience market between May 23 and June 10 (odds ratio (OR)
cannot be calculated; 95% confidence interval (CI)=3.4-infinity).
No other food-consumption or exposure category (including social
events, restaurants, grocery stores, or international travel) was
statistically associated with illness. The 18 other patients had
also consumed the ice-slush beverage.

The ice-slush beverage mixture was prepared daily with tap
water from a bathroom sink using utensils stored beside a toilet.
All five employees of the market denied having hepatitis
symptoms; four of these were tested and were negative for IgM
antibody to hepatitis A virus (IgM anti-HAV). The fifth employee,
who was one of the two persons who prepared the ice-slush
beverage, refused to be tested. However, a household contact of
this employee had had serologically confirmed hepatitis A in
early June and reported that the employee had been jaundiced
concurrently with her illness.Florida

In August 1988, the Alabama Department of Public Health noted
an increase in cases of serologically confirmed hepatitis A in
persons living in several areas of the state. Within 6 weeks
before onset of illness, most affected persons had eaten raw
oysters harvested from coastal waters of Bay County, Florida. The
Florida Department of Health and Rehabilitative Services (FDHRS)
contacted state health departments in neighboring and other
states about hepatitis A cases in July or August 1988 in persons
who had attended events serving seafood within 10-50 days of
becoming ill. The 61 persons who were identified resided in five
states: Alabama (23 persons), Florida (18), Georgia (18), Hawaii
(one), and Tennessee (one). Patients ranged in age from 8 to 60
years (median: 31 years); all were white, and 49 (80%) were male.
Fifty-nine (97%) had eaten raw oysters; one, raw scallops; and
one, baked oysters. All the oysters and scallops were traced to
the same growing area of Bay County coastal waters. The median
incubation period between consumption of raw oysters and onset of
illness was 29 days (range: 16-48 days).

To further study oyster consumption as a potential risk factor
for hepatitis A, the FDHRS conducted a case-control study using
uninfected eating companions of the patients as controls.
Fifty-three patients who had serologically confirmed hepatitis A
and 64 controls were interviewed by telephone; 51 (96%) of the
patients and 33 (52%) of the controls had eaten raw oysters
(OR=24; 95% CI=5.4-252.6). Consumption of other seafoods (i.e.,
clams, mussels, and shrimp) was not statistically associated with
illness.

The implicated oysters apparently had been illegally harvested
from outside approved coastal waters of Bay County. Sources of
human fecal contamination were identified near oyster beds
unapproved for harvesting and included boats with inappropriate
sewage disposal systems and a local sewage treatment plant with
discharges containing high levels of fecal coliforms.North
Carolina

Beginning September 30, 1988, hepatitis A cases among employees
of businesses located in east Greensboro were reported to county
health departments in central North Carolina. Only day-shift
employees became ill. Preliminary investigation suggested a
common exposure to one nearby restaurant (restaurant A), which
served as many as 400 meals per day to regular clientele. A total
of 32 outbreak-associated cases was eventually reported.

The North Carolina Department of Human Resources conducted a
case-control study to assess a possible association between
illness and exposure to restaurant A. Twenty-seven patients and
50 controls (randomly selected from co-workers) were interviewed
about exposures to different restaurants since August 15.
Patients were more likely than controls to have eaten at
restaurant A (OR=4.1; 95% CI=1.3-14.4). No other restaurant was
statistically associated with illness.

Based on additional information obtained from 16 patients and
20 controls who reported eating lunch at restaurant A 2-6 weeks
before the outbreak, only consumption of iced tea (OR=8.1; 95%
CI=0.8-387.8) or hamburgers (OR=11.4; 95% CI=1.1-551.3) was
associated with illness. However, 15 (94%) of the ill persons
drank iced tea, whereas only six (38%) of the ill persons
reported eating hamburgers.

All foodhandlers at the restaurant were tested for IgM
anti-HAV; one employee, who was IgM anti-HAV-positive, denied
symptoms of and risk factors for hepatitis A. However, this
employee was a suspected intravenous (IV)-drug user and had job
tasks that included preparation of fountain drinks and
sandwiches.

Immune globulin (IG) was given to all foodhandlers at the
restaurant. Because primary/secondary-case status and
infectiousness of the IgM anti-HAV-positive foodhandler were
unknown and because her hygiene and foodhandling practices were
questionable, the local health department recommended
administration of IG to all patrons who had eaten at the
restaurant within 2 weeks before the association between
hepatitis A and the restaurant had been determined. More than
1000 IG doses were given. The restaurant voluntarily closed for
24 days, and no persons with hepatitis A were identified with
onset after November 8.Washington

In May 1989, the Seattle-King County Department of Public
Health (SKCDPH) received reports of and investigated 213 cases of
hepatitis A--a threefold increase over the average of 68 cases
reported in each of the first 4 months of 1989. Onsets of illness
clustered during April 28-May 5. One hundred seventeen (55%) of
the patients had eaten at one outlet of a Seattle-area restaurant
chain (chain A). One of the patients was a recent employee and
three were current employees of three of the chain's restaurants.
Interviews with past and present chain A employees did not
identify any worker with illness during the period of likely
exposure for most patients (2-6 weeks before onset of illness).
All other current workers in the three restaurants were tested
for IgM anti-HAV. None were positive, and all were given IG.
Because two of the ill employees had poor hygiene and had worked
while ill with diarrhea, the SKCDPH recommended IG for patrons
who had eaten at two of the restaurants from May 3 through May 6.

The SKCDPH conducted a case-control study to further examine
the potential role of chain A restaurants in the outbreak.
Sixteen patients were randomly selected and re-interviewed by
telephone; 16 age-group- and sex-matched controls were obtained
by increasing each patient's telephone number by one. Exposure to
11 multi-outlet restaurant chains (including chain A) was
ascertained for patients during the 2-6 weeks before onset and
for controls during April 14-May 12. Mean total of any restaurant
visits was higher among patients (7.7) than among controls (4.3).
In addition, patients (89%) were more likely than controls (25%)
to have eaten at restaurants from chain A (OR=11.0; 95%
CI=2.2-56.0); differences in exposure to the 10 other
multi-outlet restaurants were not statistically significant.

Editorial Note

Editorial Note: The outbreaks reported here illustrate two
principal modes of transmission associated with foodborne
hepatitis A outbreaks: 1) contamination of food during
preparation by a foodhandler infected with hepatitis A virus and
2) contamination of food, such as shellfish, before it reaches
the food service establishment.

Contamination of food during preparation by a hepatitis
A-infected foodhandler is the most common mode of transmission in
foodborne outbreaks. The Alaska and North Carolina outbreaks are
atypical in that ice or drinks as vehicles are rare; usually the
vehicles are sandwiches or green salads that are not cooked or
are improperly handled after cooking. The outbreak in North
Carolina is also consistent with a nationwide phenomenon of
increased reports of hepatitis A among IV-drug users (2), who can
become sources of foodborne outbreaks if they are also
foodhandlers.

Contamination of food with virus before the food reaches the
service establishment is less common. Shellfish filter large
quantities of water during feeding and in the process can
concentrate microorganisms, including enterically transmitted
viruses such as hepatitis A (3). Transmission to humans occurs
when contaminated shellfish are consumed raw or undercooked.
Hepatitis A outbreaks attributed to consumption of contaminated
shellfish have been reported intermittently in the United States
and abroad (4-8); in 1988, an outbreak associated with clams
involved more than 250,000 cases in Shanghai, People's Republic
of China (7). The Florida outbreak reported here is the largest
attributed to shellfish in the United States since 1973 (4) and
the largest ever reported in Florida. Outbreaks due to pre-retail
contamination of products other than shellfish have rarely been
reported. In 1988, a multifocal outbreak linked to lettuce
possibly contaminated before local distribution occurred in
Louisville, Kentucky (9).

Measures to prevent foodborne hepatitis A outbreaks include
training of food handlers regarding proper hygiene and
foodhandling practices, investigation of food handlers who have
symptoms of hepatitis or are otherwise ill, prompt reporting by
health-care providers to local health departments of patients
with suspected foodborne hepatitis A, and prompt investigation by
health departments of possible sources of infection. Consistent
maintenance of good handwashing and other personal hygiene
measures by foodhandlers is important because the source patient
in foodborne outbreaks is often asymptomatic (as apparently
occurred in North Carolina and Alaska). Prevention of hepatitis A
outbreaks associated with shellfish relies on surveillance of
water beds where shellfish are harvested to ensure that there is
no evidence of fecal contamination. Transmission and infection
from shellfish also can be prevented by thorough cooking and
proper storage and handling before and after cooking.

When a foodhandler is diagnosed with hepatitis A, IG is usually
recommended for other foodhandlers at the same establishment
(10). IG is generally not recommended for patrons because
common-source transmission is infrequent; however, it may be
considered if the infected person handles high-risk foods, has
poor hygiene, or has diarrhea during the early stages of illness
and if patrons can be identified and treated within 2 weeks after
exposure (10). Once a foodborne hepatitis outbreak has occurred,
it is usually too late to prevent further cases because the
2-week period after exposure during which IG is effective has
already passed. The increasing number of hepatitis A cases
nationwide underscores the importance of focusing on food
handlers with hepatitis A and decisions regarding IG
administration to food service patrons.

References

CDC. Hepatitis surveillance report no. 52. Atlanta: US

Department of Health and Human Services, Public Health Service,
1989:19-21.

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